Data transmitting apparatus, receiving apparatus, and data transmission and reception system

ABSTRACT

Video and audio data of a plurality of received programs and a common information ECM are recorded to a recording medium. A recording position of the program is written on a management table. When reproducing a desired one of the recorded programs, the ECM is also reproduced together with the video and audio data. The data to retrieve the desired program and an individual information EMM are transmitted through a broadcasting wave. To descramble the reproduced video and audio data, the reproduced ECM and the received EMM are used. Since the individual information EMM is the latest information, even if there is a time lag between the recording time point and the reproducing time point, the reliability of the conditional access is not deteriorated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a data transmitting apparatus, a receivingapparatus, and a data transmission and reception system for recordingdigital data which is transmitted via, for example, a digital satellitebroadcasting onto a storage medium.

2. Description of the Related Art

Recently, a digital broadcasting system for transmitting multimedia datasuch as image signal, audio signal, and the like by using acommunication satellite has been being put into practical use. Theinvention can be applied to such a digital broadcasting system. FIG. 4shows an outline of a typical digital broadcasting system. Thetransmission side of a program is made up of an up-link station, aprogram provider, and a management system.

Video and audio data from a program provider 101 is supplied to anencoder and multiplexer 103 of the MPEG (Moving Pictures Expert Group) 2of an up-link station 102. In the MPEG 2 encoder and multiplexer 103,the video and audio data is compressed and the compressed video andaudio data is stored in a packet of a length of 188 bytes. A pluralityof programs and the packets of the respective corresponding video andaudio data are multiplexed, so that a transport packet of the MPEG2 isformed. A transport stream is formed by a series of transport packets.The number of transport streams corresponds to the number oftransponders installed in the communication satellite.

The MPEG2 transport stream is supplied to a transmission system 104. Inthe transmission system 104, processes such as scrambling process ofevery packet, error correction encoding of every packet, modulation, andthe like are executed and a modulation output is supplied to atransmitting antenna 105. The scrambling process is necessary to realizea conditional access which is used to control about the permission orinhibition of the monitoring every viewer. In the scrambling process,for example, a contract of a pay-per-view in which only a certainprogram is monitored with a toll every time can be made. A key todescramble is supplied from a key management system 106 to the MPEG2encoder and multiplexer 103 and has been inserted as one of the packetsinto the transport stream in a manner similar to the video and audioinformation.

An integrated management of the MPEG2 packets is performed by a programmanagement system 107. The program management system 107 and keymanagement system 106 are unified, thereby encrypting the key todescramble. Further, in a customer management system 108, itemsregarding a monitor contract or the like are managed. Viewer informationis transmitted and received betweem the customer management system andthe home of the viewer via a telephone line 109.

A broadcasting radio wave transmitted from the transmitting antenna 105through a communication satellite 110 is received by a receiving antenna111 at each home. A receiver 112 is connected to the receiving antenna111. The receiver 112 is constructed by a tuner for designating areceiving transponder, a demodulating unit, a descrambling unit fordescrambling, a demultiplexer for designating a packet to be separated,a video decoding unit, an audio decoding unit, and the like. The decodedvideo and audio signals are supplied to a television receiver 113.

A key for descrambling is encrypted and transmitted as concernedinformation together with video and audio signals. The key to decryptthe encryption has been stored in an IC card 114 inserted in thereceiver 112. Which program can be descrambled can be controlled fromthe transmission side on the basis of contract-information of eachreception system. The receiver having a conditional accessing functionis usually called an IRD (Integrated Receiver/Decoder).

The above digital satellite broadcasting system is not limited to anapplication field such that a television broadcasting is merelymonitored but can be also used as a transmission system of digital dataof a large capacity by many channels. That is, the receiver of thedigital satellite broadcasting can have a function as a receivingapparatus of digital data such as video and audio data, data for acomputer, or the like.

As one of using methods of the digital satellite broadcasting, there isconsidered a method whereby by combining a receiver and a recordingmedium of a large capacity, a large quantity of reception data can beaccumulated. For example, the reception data is recorded at night when atransmitting line is relatively free, and a desired portion isreproduced from the recorded data later. As a recording medium of alarge capacity, a digital VCR, a hard disk, an optical disk, asemiconductor memory, or the like can be used.

In the digital satellite broadcasting, although a form in which amonitor contract is made on a channel unit basis, a form (pay-per-view)in which a fee of only the monitored programs is paid, and the likeexist, it is-generally a toll broadcasting and the conditional access isused. Therefore, according to the method whereby reception data haspreviously been stored in the memory of the large capacity and thedesired program is reproduced later, it is irrational that all of theprograms which are stored are charged. The programs which wereselectively read out from the memory and were reproduced are charged.

The monitor control in the toll broadcasting system is performed by ascramble authorization system. In this system, individual information(EMM: Entitlement Management Message) that was formed on thetransmission side and is peculiar to the receiving terminal is sent tothe viewer. On the receiving terminal, the EMM of the same ID as the ownID is decrypted, and a work key is fetched into the IC card. The key todecode the EMM is a key which is individual for each receiving terminaland has previously been stored in the IC card. Further, a contractedchannel ID and a contract type (temporary contract, pay-per-view, or thelike) in addition to the work key are included in the EMM.

When a program is monitored, common information (ECM: EntitlementControl Message) which is accompanied with the program and is common forthe receiving terminals is fetched into the IC card. If the work keycorresponding to this channel has previously been stored, a descramblingis performed and can be monitored. The EMM and the common information(hereinafter, referred to as an ECM) are transmitted in a form of thepacket of the transport stream of the MPEG2 in a manner similar to thevideo and audio data. In case of the pay-per-view, the monitorinformation is periodically up-loaded through the telephone line.

In the foregoing toll broadcasting system, as one of methods ofrealizing a method whereby the recording medium (large capacity memory)is combined to the receiver and a desired one of the programs stored inthe recording medium is selectively reproduced and only the reproducedprogram is charged, a method of recording the EMM and ECM as well to therecording medium is also considered. The video and audio data of aplurality of programs are recorded in a scrambled state (form of thepacket) on the recording medium, the video and audio data which wasselectively reproduced is descrambled by the system of the receiver, andis further decoded. In order to enable the descrambling, the EMM and ECMare recorded to the recording medium.

However, a time lag exists between the timing when recording thereception data to the recording medium and the timing when reproducingit later. There is a possibility such that the EMM which is individualfor each receiving terminal is changed due to a change or the like incontract. Thus, according to the system for recording the EMM at thattime point together with the data of the program, there occurs a fearsuch that the reliability of the conditional access is deteriorated. Forexample, upon recording, although the customer which is instructed inthe EMM has a right corresponding to the rank of the recorded program,at the time of point of reproduction, even if the right has already beenterminated due to the elapse of the validity term, the right isauthorized on the EMM which has already been recorded. In an extremecase, a situation such that the right which was validated by the latestEMM is invalidated by the reproduced old EMM also occurs.

OBJECTS AND SUMMARY OF THE INVENTION

It is, therefore, an object of the invention, to provide a datatransmitting apparatus, a receiving apparatus, and a data transmissionand reception system which can prevent a situation such that thereliability of a conditional access is deteriorated by controlling thereproduction of recorded data by latest individual information.

According to the invention, to solve the foregoing problems, there isprovided a data transmitting apparatus for transmitting multiplexeddigital data, characterized by comprising:

means for encrypting a plurality of information data;

means for transmitting first control data which is used to decrypt theencryption and is common to receiving terminals and second control datawhich is used to decrypt the encryption and is individual for thereceiving terminals together with the plurality of encrypted informationdata; and

means for transmitting data necessary to retrieve the plurality ofinformation data and the present second control data after the pluralityof encrypted information data was transmitted.

According to the invention, there is also provided a data receivingapparatus for receiving multiplexed digital data, characterized in that

a plurality of encrypted information data, first control data which isused to decrypt the encryption and is common to receiving terminals, andsecond control data which is used to decrypt the encryption and isindividual for the receiving terminals are included in a receptionsignal,

and the apparatus comprises:

a recording medium for recording the plurality of encrypted informationdata and the first control data;

managing means for instructing a recording position of each of theplurality of information data on the recording medium;

means for reproducing desired information data and the first controldata from the recording medium with reference to the managing means; and

means for decrypting the reproduced information data by using thereproduced first control data and the present second control datareceived.

According to the invention, there is further provided a datatransmission and reception system for transmitting multiplexed digitaldata and receiving the multiplexed digital data, characterized in that

an apparatus on the transmission side comprises:

means for encrypting a plurality of information data; and

means for transmitting first control data which is used to decrypt andis common to receiving terminals and second control data which is usedto decrypt and is individual for the receiving terminals together withthe plurality of encrypted information data,

and an apparatus on the reception side comprises:

a recording medium for recording the plurality of encrypted informationdata and the first control data,

managing means for instructing a recording position of each of theplurality of information data on the recording medium;

means for reproducing desired information data and the first controldata from the recording medium with reference to the managing means; and

means for decrypting the reproduced information data by using thereproduced first control data and the present second control datareceived.

According to the transmitting apparatus of the invention, since the datafor retrieving a plurality of information data and the second controldata EMM are transmitted, the plurality of information data can beeasily retrieved on the reception side. Since the encryption isdecrypted by the latest EMM on the reception side, the reliability ofthe conditional access is not deteriorated. In the receiving apparatus,the plurality of information data received and the first control dataECM are recorded to the recording medium and the reproduced firstcontrol data ECM and the received second control data EMM are used todecrypt the information data which was selectively reproduced, so thatthe deterioration of the reliability of the conditional access can beprevented.

The above, and other, objects, features and advantage of the presentinvention will become readily apparent from the following detaileddescription thereof which is to be read in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a construction of an embodiment of theinvention;

FIG. 2 is a block diagram showing a construction mainly about themonitor control in the embodiment of the invention;

FIG. 3 is a schematic diagram for explaining the retrieving operation inthe embodiment of the invention; and

FIG. 4 is a schematic diagram showing an outline of a typical digitalbroadcasting system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention will now be described hereinbelow withreference to the drawings. FIG. 1 is a block diagram showing theembodiment. A receiving antenna shown at 1 receives a radio wave from acommunication satellite (or broadcasting satellite). A converterassociated with the antenna 1 down-converts the reception signal into afirst IF (intermediate frequency) signal of a predetermined frequencyand generates to a tuner 2.

In the tuner 2, a receiving channel (namely, receiving transponder) setby the user is selected and a second IF signal is formed. The second IFsignal is supplied to a demodulating unit 3 and, for example, a QPSK isdemodulated. A demodulation output from the demodulating unit 3 issupplied to an error correcting unit 4. The error correcting unit 4corrects errors occurring during the transmission by an error correctioncode such as a Reed Solomon code. An output (transport stream) of theerror correcting unit 4 is supplied to a descrambling unit 5. In thedescrambling unit 5, a descrmable to cancel the scramble is performed.

The transport stream of the MPEG2 which is an output of the descramblingunit 5 is supplied to a separating unit 6. In the separating unit 6, thepacket of a desired channel is separated from the transport stream. Itis also separated into video data, audio data, and control data (the ECMand EMM and the like are included) on the basis of information of aheader portion. Further, a switching between the data of the receivedprogram and the data of the program which was selectively reproducedfrom the recording medium is also performed.

The video data from the separating unit 6 is decoded by a video decodingunit 7V and a reception video signal is generated. The audio data isdecoded by an audio decoding unit 7A and a reception audio signal isgenerated. The control data (including the EMM and ECM) is supplied toan apparatus control unit 10. The decoded video signal is added with asignal for display by an-adder 16. An output video signal of the adder16 is displayed on a display (not shown). Similarly, the decoded audiosignal is, for instance, amplified by an amplifier and outputted from aspeaker (not shown). A PID is added to the transport packet and atransmission destination (video decoding unit 7V, audio decoding unit7A, or apparatus control unit 10) of the packet is instructed by thePID.

The apparatus control unit 10 controls the operation of the wholereceiver and is constructed by a microcomputer. The tuner 2, an IC card11, a flash memory 12, an RAM 13, a user interface 14, and a screendisplay forming unit 15 are connected to the apparatus control unit 10.Further, bit error rate information is supplied from the errorcorrecting unit 4 to the apparatus control unit 10. Since a bit errorrate has a correlation with a C/N ratio, the apparatus control unit 10can know a radio wave situation (C/N ratio) from the bit error rateinformation. A degree of C/N ratio can be displayed on the screen of thedisplay. Thus, the adjustment of the direction of the antenna,permission or inhibition of the down-loading of the program, and thelike can be controlled.

The user interface 14 is keys on a front panel, a pointing device suchas screen display, mouse, or the like, a remote control system, or thelike. Although not shown, a modem is connected to the apparatus controlunit 10 and viewer information is transmitted via the telephone line.

A program for controlling the ordinary operation is stored in the flashmemory 12. The control of the ordinary operation which is executed bythe apparatus control unit 10 is executed on the basis of the programstored in the flash memory 12. The RAM 13 is used as a temporary storingunit when rewriting the flash memory 12. The screen display forming unit15 forms various display signals under the control of the apparatuscontrol unit 10. The display signals are supplied to the adder 16 andmultiplexed to the decoded video signal.

A recording medium 20 is connected to the receiver through a digitalinterface 22 in order to record the data of a plurality of programsreceived by the receiver by using free time such as at night or the likeas mentioned above and to selectively reproduce a desired program amongthem after that. As a recording medium 20, a medium of a large capacityis preferable and a digital VCR (video cassette tape recorder), a harddisk, an optical disk, or the like can be used. A management table 21 isused in association with the recording medium 20. The management table21 shows a corresponding relation between the recorded data, forexample, an ID (program number) of the program and information of itsrecording position. Although a control unit, a mechanism unit, and thelike are provided in association with the recording medium 20, they arenot shown for simplicity of explanation.

As a management table 21, an area on the same medium as that of therecording medium 20 can be used or an area on another medium can be alsoused. For example, in case of the digital VCR, the management table canbe constructed in a semiconductor memory built in a cassette or asurface of the cassette. In case of the semiconductor memory, adirectory area on the memory can be used.

The previous data of the descrambling unit 5, namely, the video andaudio data in the scrambled state is recorded on the recording medium 20through the digital interface 22. The apparatus control unit 10 anddigital interface 22 are connected and the ECM associated with the videoand audio data of the program to be recorded is also recorded. Since theECM and EMM are information for control, they are not scrambled.However, the EMM as individual control data is not recorded in thereceiver. This is because the EMM received at the newest real time is tobe used as the EMM.

Further, control information necessary to record and reproduce the datato/from the recording medium 20 is also transmitted from the apparatuscontrol unit 10 through the digital interface 22. The reproduced data,namely, the video data and audio data of the selected program aresupplied to the descrambling unit 5 through the digital interface 22.The reproduced ECM associated with the selected program is supplied tothe apparatus control unit 10 through the digital interface 22. By usingthe reproduced ECM and the received present (namely, latest) EMM, theapparatus control unit 10 generates a scramble key that is necessary fordescrambling the reproduced video and audio data. Thus, the descrambledvideo and audio data is obtained.

Although the digital satellite broadcasting system is constructed in amanner similar to that shown in FIG. 4, a more detailed constructionmainly about the monitor control in the toll broadcasting is shown inFIG. 2. FIG. 2 shows a transmission side system and a reception sidesystem. Both systems are connected by a transmission path 31 including acommunication satellite, a broadcasting satellite, and the like and atelephone line 32 to up-load the monitor information.

The transmission side system will now be described. An encoder 33converts the video signal and audio signal into digital signals andcompresses the digital signals. Specifically speaking, for example, anMPEG2 encoder is used. An output of the encoder 33 is supplied to amultiplexing unit 34. In the multiplexing unit 34, the output of theencoder 33 and the control information are time-division multiplexed. Ascrambling unit 35 scrambles the digital information by the scramblekey. The EMM and ECM serving as control information are not scrambled.

The EMM is transmitted to the individual receiver and the ECM is theinformation associated with the program and they are the signals whichare commonly transmitted to the program receiver. In a concernedinformation transmitting unit 36, the scramble key is encrypted by thework key and is transmitted as a part of the ECM. The work key isencrypted in a scramble management system 37 by an individual keypeculiar to the receiver and is transmitted as a part of the EMM. In thescramble management system 37, the individual key is stored incorrespondence to all of the receivers. That is, the scramble managementsystem 37 receives the data of the EMM from a customer management system38 and encrypts the data. In the scramble management system 37, a cardID, the individual key, and all of the circulated work keys are stored.A card ID and an individual key are newly generated and transferred toan IC card issuer, thereby allowing an IC card to be formed.

A customer management system 38 processes the monitor information whichis up-linked from a number of receivers and contract requests from theviewers and transfers the contract information to the scramblemanagement system-37. A program management system 39 controls theencoder 33 by the control signal in accordance with the program. And theprogram management system 39 generates a program number or the like, andsupplies to the concerned information transmitting unit 36. Theconcerned information transmitting unit 36 mainly receives the ECM andencrypts.

On the receiver side, the EMM is previously fetched to an IC card 41(shown at reference numeral 11 in FIG. 1) as one of security modules andis decoded by the EMM recorded in the IC card 41. The work key is takenout and stored in the IC card 41. The contract information in the EMM isstored.

In case of receiving a certain program, the receiver reads the ECMassociated with the program into the IC card 41 and is collated with thecontract information which has previously been fetched. If the receivedprogram is the contracted program, the scramble key in the ECM isdecoded by using the work key and sent to a decoder 42. In the decoder42, a descrambling is performed by an internal descrambling unit.

In case of the pay-per-view contract, a monitor career is stored in theIC card 41. After the elapse of a predetermined period, the monitorcareer is up-linked as monitor information to the customer managementsystem 38 of the transmission side system through a telephone modem inthe decoder 42. The IC card uses, for example, an 8-bit CPU of one chip.The individual key and the ID have been written in an EEPROM in the chipand cannot be rewritten by the user. The monitor information is alsowritten in the EEPROM.

The control of the monitor control system in the toll broadcastingmentioned above will now be described. The descrambling is constructedby processes of three stages. First, the work key is decoded from theEMM by using the individual key of the receiver. Subsequently, thescramble key is decoded from the ECM by using the work key. The videodata and audio data are descrambled by using the decoded scramble key.

When explaining in more detail, the EMM is transmitted to the viewer whonormally made a contract, the encryption is decrypted by the firstdecoder, and the work key is stored into the IC card 41. The key whichis used in the decoding is the key that is individual for each receiver.The individual key has previously been stored in the IC card 41. In thetransmission side system, as mentioned above, the individual keys of thereceivers and all of the ID numbers have been stored and the encryptedEMM is transmitted by using the individual key corresponding to the IDnumber of the receiver to be transmitted. The ID number has-been addedto the non-encrypting portion of the EMM. In the receiver, the ID numberis compared with the ID in the IC card 41. Only the EMM in which thoseIDs coincide is fetched into the IC card 41 and used.

When the program is monitored, the ECM associated with the program isfetched to the IC card 41. If the work key corresponding to the channelhas previously been stored, the second decoder operates and the scramblekey is obtained. The scrambled program signal is descrambled in thedescrambling unit and is outputted as a signal which can be normallymonitored.

Information of the work key, contracted channel ID, and contract type(temporary contract, pay-per-view, or the like) is included in the EMM.The work key is sent together with the key number and a plurality ofwork keys can be selectively used.

According to the embodiment of the invention, in a plurality of receivedprogram data, the packet of the video data and the packet of the audiodata of the scrambled information and the ECM associated with theprogram are stored into the recording medium 20 through the digitalinterface 22. In this case, a corresponding relation between the programnumber as an ID of the program and the recording position of the programon the recording medium 20 is also recorded in the management table 21concerned with the recording medium 20. The EMM having a possibilitysuch that it will be changed in future by a change in contractedcontents or the like is not recorded onto the recording medium 20.

After the recording to the recording medium 20, data for retrieving(browsing) the recorded information data is transmitted from an up-linkstation to the receiver. At the same time, the EMM as an individualinformation is also annexed and transmitted to the viewer who recordedthe program. Processes in case of selectively reproducing the desiredprogram from the recording medium 20 will now be described withreference to FIG. 3.

By the data for browsing sent from the up-link station to the viewer,contents as shown at 51 in FIG. 3 are displayed on the display of theviewer. That is, characters showing the contents 52 of the plurality ofrecorded programs and the buttons 53 for selection are included. Thedisplay 51 shown in FIG. 3 is one example. As another example, so longas a display such that the contents of the recorded programs aredisplayed and a desired one of the recorded programs can be selected,various displays can be used. The browser (software) has previously beenstored as a program in the ROM of the receiver or is transmitted throughthe broadcasting wave and is down-loaded into the memory which isconnected to the apparatus control unit 10.

The viewer designates a desired program to be reproduced by using amouse or the like in the display 51 for browsing. When a certain programis designated, the program number corresponding to the program issupplied from the apparatus control unit 10 to the management table 21through the digital interface 22, for example. As shown in FIG. 3,recording positions (start addresses ST1, ST2, . . . , and end addressesEN1, EN2, . . . ) on the recording medium 20 of program numbers X1, X2,. . . of the programs recorded on the recording medium 20 have beenwritten in the management table 21. Therefore, by referring to themanagement table 21, the recording position of the program numberdesignated in the display 51 of the browsing can be known.

The information of the desired program number and the correspondingrecording position is sent to the recording medium 20 (more specificallyspeaking, reading or reproduction control unit). Thus, the video packet,audio packet, and ECM of the program of the desired program number arereproduced. The reproduced information is transmitted to the apparatuscontrol unit 10 through the digital interface 22. In the apparatuscontrol unit 10, the scramble key is generated as mentioned above byusing the received latest EMM and the reproduced ECM. In thedescrambling unit 5, the video packet and audio packet of the selectedprogram are descrambled by using the scramble key. The separating unit 6is controlled by the apparatus control unit 10 so as to select the dataof the reproduced program. In a manner similar to the ordinary receivedprogram, the program by the reproduction data of the recording medium 20can be monitored.

Although the example of transmitting the video and audio data throughthe broadcasting wave has been described above, the invention can bealso applied to a system for transmitting the video and audio data by aradio transmission other than the broadcasting wave. Only one of thevideo data and the audio data can be also transmitted. Further, data ofa computer program can be also transmitted without limiting to the videoand audio data.

By transmitting the data for retrieval to the viewer after therecording, the viewer can easily perform the selecting operation of thedesired program.

Having described a specific preferred embodiment of the presentinvention with reference to the accompanying drawings, it is to beunderstood that the invention is not limited to that precise embodiment,and that various changes and modifications may be effected therein byone skilled in the art without departing from the scope or the spirit ofthe invention as defined in the appended claims.

What is claimed is:
 1. A transmitting apparatus for a digitalbroadcasting system for controlling access to scrambled programs basedon a customer's most recent account information, comprising: ascrambling unit for scrambling a program using a first encryption key;said first encryption key being specific to said program and generic toa plurality of receiving apparatuses; the scrambled program requiringboth said first encryption key and a second encryption key to beunscrambled; a first transmitter for transmitting the scrambled programalong with the corresponding first encryption key to said plurality ofreceiving apparatuses; and a second transmitter for transmitting saidsecond encryption key to a specific receiving apparatus in response to arequest therefrom; said second encryption key being generic to aplurality of programs and specific to said specific receiving apparatus;said second encryption key being determined and updated periodically onthe basis of said customer's present account information.
 2. A receivingapparatus for a digital broadcasting system for controlling access toscrambled programs based on a customer's most recent accountinformation, comprising: a first receiver for receiving a scrambledprogram and a corresponding first encryption key from a transmittingapparatus; said first encryption key being specific to said program andgeneric to a plurality of receiving apparatuses; a transmitter forperiodically requesting a second encryption key from said transmittingapparatus; a second receiver for receiving said second encryption keyfrom said transmitting apparatus; said second encryption key beinggeneric to a plurality of programs and specific to said receivingapparatus; said second encryption key being determined and updatedperiodically on the basis of said customer's present accountinformation; a recorder for recording said scrambled program and saidcorresponding first encryption key; said recorder also for recording thesecond encryption key most recently received from said transmittingapparatus; a decoder for unscrambling said scrambled program using thecorresponding first encryption key and the most recent second encryptionkey; said scrambled program and first encryption key being selectivelyprovided by said first receiver or said recorder; and reproducing meansfor reproducing a program unscrambled by said decoder.
 3. The receivingapparatus according to claim 2, further comprising managing means formanaging a plurality of scrambled programs and corresponding firstencryption keys recorded by said recorder.
 4. A digital broadcastingsystem for controlling access to scrambled programs based on acustomer's most recent account information, comprising: a transmittingapparatus for transmitting programs to a plurality of receivingapparatuses, comprising: a scrambling unit for scrambling a programusing a first encryption key; said first encryption key being specificto said program and generic to said plurality of receiving apparatuses;the scrambled program requiring both said first encryption key and asecond encryption key to be unscrambled; a first transmitter fortransmitting the scrambled program along with the corresponding firstencryption key to said plurality of receiving apparatuses; and a secondtransmitter for transmitting said second encryption key to a specificreceiving apparatus in response to a request therefrom; said secondencryption key being generic to a plurality of programs and specific tosaid specific receiving apparatus; said second encryption key beingdetermined and updated periodically on the basis of said customer'spresent account information; and at least one of said plurality ofreceiving apparatuses, comprising: a first receiver for receiving thescrambled program and corresponding first encryption key from saidtransmitting apparatus; a third transmitter for periodically requestingsaid second encryption key from said transmitting apparatus; a secondreceiver for receiving said second encryption key from said transmittingapparatus; a recorder for recording the scrambled program andcorresponding first encryption key; said recorder also for recording thesecond encryption key most recently received from said transmittingapparatus; a decoder for unscrambling said scrambled program using thecorresponding first encryption key and the most recent second encryptionkey; said scrambled program and first encryption key being selectivelyprovided by said first receiver or said recorder; and reproducing meansfor reproducing said program unscrambled by said decoder.
 5. The digitalbroadcasting system according to claim 4, wherein said programs aredigital television programs.
 6. The digital broadcasting systemaccording to claim 4, wherein said recorder and said reproducing meansare a digital VCR.